Is template parsing happening at compile time or at runtime of the GO code?

Question

go

Please do not kick much, I just like to know how it works inside and how to optimize and speed it up.
Explain how template parsing works internally.
Which option is better in terms of performance and resources.
Option 1 - Global variable

var t, err = template.ParseFiles("templates/wt/index.html", "templates/wt/header.html", "templates/wt/footer.html")
  
func main(){

}

func indexHandler(w, r){
  t.ExecuteTemplate(w, "index", locale)
}

Option 2 - In the main function

func main(){
  t, err := template.ParseFiles("templates/wt/index.html", "templates/wt/header.html", "templates/wt/footer.html")
}

func indexHandler(w, r, t){
  t.ExecuteTemplate(w, "index", locale)
}

Option 3 - In a processed function

func main(){
  
}

func indexHandler(w, r){
  t, err := template.ParseFiles("templates/wt/index.html", "templates/wt/header.html", "templates/wt/footer.html")
  t.ExecuteTemplate(w, "index", locale)
}

Answer 1

In the first option, how will you handle errors?
In the third option, for each request, files with templates will be opened and parsed.